In general, it is common knowledge that by increasing overall rigidity of large planar sections of an engine or compressor block, the noise emitted therefrom can be reduced. However, excess material increases weight and reduces the weight to horsepower ratio for highway applications. Furthermore, excess material increases component costs. One concept to increase rigidity is discussed in a paper by Priede, Grover and Lalor, published in The Society of Automotive Engineers Journal, Paper No. 450, 1969. The paper suggests the use of a crank frame and crank beam structure to reduce engine block deformation which consequently causes a reduction in noise. A major problem of such a structure as disclosed in the paper is that a radical engine redesign is required. Such a design would require a total revision of the existing engine concept. Therefore, use of such a concept is unrealistic for adapting to an existing engine design.
U.S. Pat. No. 3,841,203 to Glenister Bruce issued Oct. 15, 1974 discloses a rigid beam bolted to the bearing caps and the block sidewalls of an engine or compressor to improve crankshaft and crankcase stiffness. The beam is attached to the main bearing caps by an outer retaining bolt after the caps have been assembled and secured to the crankcase by two inner retaining bolts. The stiffening beam is shown attached to a vertical inner side of the block and secured by a bolt. The beam is also shown abutted against the flat horizontal lower face of the block skirt. Furthermore, the beam is always secured to the bearing caps. The securing of the beam to the bearing caps adds an unnecessary limitation to the structure which is not required when adding rigidity to most existing engine structures. For example, the structure requires additional machining and assembly time, reduces serviceability, and adds cost to the design which in today's competitive world reduces sales and profits.
UK Patent Application GB No. 2 164 389A to Otmar Andres published Mar. 19, 1986 discloses a stiffening frame with cross members below detachable crankshaft bearing caps. The stiffening frame is positioned between the block and the oil pan. This concept requires a gasket between the block and frame and a gasket between the frame and the oil pan. A plurality of bolts extend through the oil pan, gaskets and frame and threadably secures the components together. Positive clamping between the frame and block is prevented by the gasket therebetween. This type of construction provides another joint which will increase the chance of eventual leaks. Aging of the gasket, fretting between associated members and vibrations between the block and gasket further contribute to the potential of such leakage.
The present invention is directed to overcoming one or more of the problems as set forth above.